This invention relates to new RAR selective retinoid agonists, to the use of such retinoic acid receptor agonists, particularly retinoic acid receptor xcex3 selective agonists (RARxcex3-selective) for the treatment of emphysema.
Chronic obstructive pulmonary disease (COPD) is a major cause of morbidity and mortality, ranking third and fourth as the leading cause of death in the European Union and North America respectively. COPD is characterized by reduced maximum expiratory flow, which does not change over several months and which persists for 2 or more consecutive years. Patients with the most severe form of COPD generally present with a significant degree of emphysema. Emphysema is defined anatomically by permanent airspace enlargement distal to the terminal bronchioles. It is characterized by gradual loss of lung recoil, alveolar destruction, decreased alveolar surface area and gas exchange, leading to a reduced FEV1. These two features, impaired gas exchange and reduction in expiratory flow, are characteristic physiological abnormalities from which patients with emphysema suffer. The main symptom of patients with severe emphysema is shortness of breath during minimal physical activity.
The most common cause of emphysema is cigarette smoking although other potential environmental toxins may also contribute. These various insulting agents activate destructive processes in the lung including release of active proteases and free radical oxidants in excess of protective mechanisms. The imbalance in protease/anti-protease levels leads to destruction of the elastin matrix, loss of elastic recoil, tissue damage and continuous decline in lung function. Removing the injurious agents (i.e. quit smoking) slows the rate of damage, however, the damaged alveolar structures do not repair and lung function is not regained.
Retinoic acid is a multifunctional modulator of cellular behavior, having the potential to alter both extracellular matrix metabolism and normal epithelial differentiation. In lung, retinoic acid has been shown to modulate various aspects of lung differentiation by interacting with specific retinoic acid receptors (RAR) that are selectively expressed temporally and spatially. Coordinated activation of RARxcex2 and RARxcex3 has been associated with lung branching and alveolization/septation. During alveolar septation, retinoic acid storage granules increase in the fibroblastic mesenchyme surrounding alveolar walls and RARxcex3 expression in the lung peaks. Depletion of these retinyl-ester stores parallels the deposition of new elastin matrix and septation. In support of this concept, Massaro et al., Am. J. Physiol., 1996, 270, L305-L310, demonstrated that postnatal administration of retinoic acid increases the number of alveoli in rats. Furthermore, the capacity of dexamethasone to prevent the expression of CRBP and RARxcex2 mRNA and subsequent alveolar septation in developing rat lung was abrogated by all-trans retinoic acid.
Recent studies demonstrated that all-trans retinoic acid can induce formation of new alveoli and return elastic recoil to near normal in animal models of emphysema, D. Massaro et el., Nature Medicine, 1997, 3, 675. However, the mechanism by which this occurs remains unclear.
Retinoids are a class of compounds structurally related to vitamin A, comprising natural and synthetic compounds. Several series of retinoids have been found clinically useful in the treatment of dermatological and oncological diseases. Retinoic acid and its other naturally occurring retinoid analogs (9-cis retinoic acid, all-trans 3-4 didehydro retinoic acid, 4-oxo retinoic acid and retinol) are pleiotropic regulatory compounds that modulate the structure and function of a wide variety of inflammatory, immune and structural cells. They are important regulators of epithelial cell proliferation, differentiation and morphogenesis in lung. Retinoids exert their biological effects through a series of hormone nuclear receptors that are ligand inducible transcription factors belonging to the steroid/thyroid receptor superfamily. The retinoid receptors are classified into two families, the retinoic acid receptors (RARs) and the retinoid X receptors (RXRs), each consisting of three distinct subtypes (xcex1, xcex2, and xcex3). Each subtype of the RAR gene family encodes a variable number of isoforms arising from differential splicing of two primary RNA transcripts. All-trans retinoic acid is the physiological hormone for the retinoic acid receptors and binds with approximately equal affinity to all the three RAR subtypes, but does not bind to the RXR receptors for which 9-cis retinoic acid is the natural ligand.
In many non-pulmonary tissues, retinoids have anti-inflammatory effects, alter the progression of epithelial cell differentiation, and inhibit stromal cell matrix production. These properties have led to the development of topical and systemic retinoid therapeutics for dermatological disorders such as psoriasis, acne, and hypertrophic cutaneous scars. Other applications include the control of acute promyelocytic leukemia, adeno- and squamous cell carcinoma, and hepatic fibrosis. A limitation in the therapeutic use of retinoids outside of cancer has stemmed from the relative toxicity observed with the naturally occurring retinoids, all-trans retinoic acid and 9-cis retinoic acid. These natural ligands are non-selective and therefore have pleiotropic effects throughout the body, which are often toxic. Recently various retinoids have been described that interact selectively or specifically with the RAR or RXR receptors or with specific subtypes (xcex1, xcex2, xcex3) within a class.
This invention provides new RAR selective retinoid agonists of formula I 
wherein
one of R4 and R5 is hydrogen and the other is 
R1 is hydrogen, lower alkyl;
R2 is lower alkyl;
R3 is lower alkyl or H;
X is oxygen or sulfur;
n is 1 or 2; and
wherein the dotted bond is optional;
and pharmaceutically active salts of carboxylic acids of formula I.
The compounds of formula I contain a chiral carbon (to which R2 is bound). These compounds may be present as a racemic mixture, i.e. (RS) or in the pure enantiomeric form as (S) or (R) isomer.
Activation of RAR has been associated with lung branching and alveolization. The retinoids according to the invention possess RAR agonist activity in vitro. Therefore such compounds would be useful for the treatment of emphysema and related pulmonary diseases. They may also be useful for the therapy and prophylaxis of dermatological disorders which are accompanied by epithelial lesions, e.g. acne and psoriasis, light- and age-damaged skin; as well as for the promotion of wound healing, for example of incised wounds, such as surgical wounds, wounds caused by burns and other wounds caused by cutaneous trauma; and for the therapy and prophylaxis of malignant and premalignant epithelial lesions, tumours and precancerous changes of the mucous membrane in the mouth, tongue, larynx, oesophagus, bladder, cervix and colon.
When the dotted bond is present, a triple bond is meant, when the dotted bond is absent a double bond. Where the xe2x80x9cdotted bondxe2x80x9d is absent, the double bond may be xe2x80x9cExe2x80x9d or xe2x80x9cZxe2x80x9d configurated. The terms xe2x80x9cExe2x80x9d and xe2x80x9cZxe2x80x9d are used herein as defined in Pure and Applied Chem. 1976, 54, 12.
The term xe2x80x9clower alkylxe2x80x9d as used herein denotes straight chain or branched alkyl residues containing 1 to 5 carbon atoms, such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert.-butyl, pentyl, amyl and 3-pentyl.
The term xe2x80x9csubstantially freexe2x80x9d of one or another isomer means that the ratio of the desired isomer to the undesired isomer is at least 95:5, more preferably at least 98:2. Resolution of the racemic mixture into either enantiomeric form can be performed in accordance with conventional techniques.
The compounds of formula I, wherein R1 is hydrogen forms salts with pharmaceutically acceptable bases such as alkali salts, e.g. Na- and K-salts, and ammonium or substituted ammonium salts such as trimethylammonium salts which are within the scope of this invention.
Preferred compounds of formula I are the compounds of formula IA 
wherein X, R1, R2, R3, n and the dotted bond are defined as above; and pharmaceutically active salts of carboxylic acids of formula IA.
Especially preferred compounds of formula IA are the compounds, wherein X is oxygen and n is 2, particularly compounds:
A 4-(5-methoxymethyl-5-methyl-2,3,4,5-tetrahydro-1-benzo[b]oxepin-8-yl-ethynyl)-benzoic acid
B 4-(5-ethoxymethyl-5-methyl-2,3,4,5-tetrahydrobenzo[b]oxepin-8-ylethynyl)-benzoic acid
C 4-(5-methyl-5-propoxymethyl-2,3,4,5-tetrahydrobenzo[b]oxepin-8-ylethynyl)-benzoic acid
D (E)-4-[2-(5-methoxymethyl-5-propyl-2,3,4,5-tetrahydrobenzo[b]oxepin-8-yl)-vinyl]-benzoic acid
E (E)-4-[2-(5-methoxymethyl-5-methyl-2,3,4,5-tetrahydrobenzo[b]oxepin-8-yl)-vinyl]-benzoic acid
F (E)-4-[2-(5-methyl-5-propoxymethyl-2,3,4,5-tetrahydrobenzo[b]oxepin-8-yl)-vinyl]-benzoic acid.
Further especially preferred are compounds of formula IA, wherein X is sulfur and n is 2, in particular the compounds:
G 4-(5-methoxymethyl-5-methyl-2,3,4,5-tetrahydrobenzo[b]thiepin-8-ylethynyl)-benzoic acid
H 4-(5-ethoxymethyl-5-methyl-2,3,4,5-tetrahydrobenzo[b]thiepin-8-ylethynyl)-benzoic acid
I (E)-4-[2-(5-ethoxymethyl-5-methyl-2,3,4,5-tetrahydrobenzo[b]thiepin-8-yl)-vinyl]-benzoic acid
J (E)-4-[2-(5-methoxymethyl-5-propyl-2,3,4,5-tetrahydrobenzo[b]thiepin-8-yl)-vinyl]-benzoic acid.
A further preferred group of compounds are the compounds of formula IB 
wherein X, R1, R2, R3, n and the dotted bond are as defined above; and
pharmaceutically active salts of carboxylic acids of formula IB.
Especially preferred compounds of formula IB are those wherein n is 1 and X is oxygen, for example the compounds:
K 4-(4-methoxymethyl-4-methyl-chroman-6-ylethynyl)-benzoic acid
L (E)-4-[2-(4-methoxymethyl-4-methyl-chroman-6-yl)-vinyl]-benzoic acid.
The compounds according to the invention can be prepared in a manner known in the art. Compounds of formula IA, wherein n is 1 or 2 and the dotted bond is present may be prepared according to the method depicted in scheme 1. 
wherein the symbols are as defined above and Hal is halogen such as iodine, bromine or chlorine.
Reaction Step 1a
A dihydrobenzo[b]oxepine- or dihydrobenzo[b]thiepine-one (1) is submitted to a Wittig-reaction with (methoxymethyl)triphenylphosphonium chloride in presence of a strong base, e.g. n-butyllithium, to form after acidic hydrolysis the aldehyde (2), the reaction is preferably carried out in a solvent as e.g. tetrahydrofuran (THF) at temperatures of about xe2x88x9278xc2x0 to 0xc2x0 C.
Reaction Step 1b
The carbaldehyde is then alkylated to (3) with an appropriate alkylhalogenide, preferably an alkyliodide in presence of a base as e.g. potassium tert.-butylate in a polar solvent, preferably in tert.-butanol. O-Alkylated side products can be separated and recycled if desired.
Reaction Step 1c
The reduction of the alkylated carbaldehyde (3) is preferably performed with sodium borohydride. The primary alcohol (4) obtained by this reduction is submitted to step 1d.
Reaction Step 1d
This etherification is preferably performed by deprotonation with a strong base as e.g. sodium hydride is a polar solvent, preferably N,N-dimethylformamide (DMF), and subsequent alkylation with an alkylhalogenide, preferably an alkyliodide.
Reaction Steps 1e, 1f and 1g
The halogenated tetrahydro-oxepine or -thiepine (5) is coupled with trimethylsilyl-acetylene in the presence of a base like piperidine or triethylamine and catalytic amounts of CuI, triphenylphosphine and bis(triphenylphoshpine) palladium (II) chloride or tetrakis-(triphenylphosphine)-palladium (0) to form the ethinylated derivative (6) (reaction step 1e).
After desilylation with catalytic amounts of sodium methylate in methanol to form compound (7) (reaction step 1f) alkyl-4-iodo-benzoate is attached by means of a second Sonogashira-coupling in the presence of a base like triethylamine and catalytic amounts of copper iodide, triphenylphosphine and bis(triphenylphosphine) palladium(II) chloride to yield the compound IA, wherein n is 2.
Reaction Step 1h
In the alternative shortcut, the halogenated tetrahydro-oxepine and -thiepine, respectively, (5) can be reacted directly with alkyl (4-ethynyl)benzoate as described in reaction step 1e in the presence of CuI, triphenylphosphine and tetrakis-(triphenylphosphine)-palladium (0) or bis-(triphenylphosphine)palladium (II) chloride to afford compound IA. However, if Hal is Br, the yields are satisfactory in the sulfur series only.
Compounds of formula IA, wherein the dotted bond is absent may be prepared according to the method depicted in scheme 2 
Reaction Step 2a
The halogenated tetrahydro-oxepine or -thiepine, respectively, (5) is reacted subsequently with butyllithium and dimethyl formamide at xe2x88x9278xc2x0 C. to yield after work-up with ammonium chloride the desired aldehyde (8).
Reaction Step 2b
The aldehyde (8) is then further elaborated via Wittig-Horner-reaction with the appropriate benzylic phosphonate in a polar aprotic solvent, preferably N,N-dimethylformamide or dimethylsulfoxide, in the presence of a strong base like sodium hydride, to afford trans-olefin IA. The Wittig-Horner reaction is highly xe2x80x9cExe2x80x9d selective, and Schemes 2 and 4 illustrate synthesis of the xe2x80x9cExe2x80x9d isomer. The corresponding xe2x80x9cZxe2x80x9d isomer may be prepared in accordance with Scheme 1 or 3, followed by Lindlar reduction of the triple bond.
Compounds of formula IB, wherein n is 1 or 2 may be prepared according to the methods depicted in reaction schemes 3 and 4. 
Whereas the compounds of formula IA can be prepared starting from meta-halogenated compounds (1), readily accessible from commercially available m-bromo-phenol and m-bromo-thiophenol, respectively; the compounds of formula IB are prepared starting from the not halogenated compounds (10), (prepared starting from phenol and thiophenol, respectively) which are functionalized at a later stage by conventional halogenation methods, see reaction step 3d. If R3=H in compounds of formulae 1A and 1B, the primary hydroxy group must be suitably protected as e.g. acetate throughout the synthesis. Finally, the ester group COOR1 of compounds of formula IA and IB can be hydrolyzed to the free acids according to standard conditions, e.g. with sodium hydroxide in THF/ethanol/acetone.
The starting compounds (1) and (10) can be made as illustrated in Scheme 5, or in analogy thereto. 
In another aspect, this invention is concerned with the use of RAR selective agonist with systemic administration being a preferred mode of delivery for treating emphysema and associated pulmonary diseases. It is thus concerned with a method for treating emphysema and associated pulmonary diseases by treatment of a mammal with a RAR selective agonist with systemic administration being a preferred mode of delivery.
A xe2x80x9ctherapeutically effective amountxe2x80x9d means the amount of a compound that, when administered to a mammal for treating or preventing a disease, is sufficient to effect such treatment or prevention for the disease. The xe2x80x9ctherapeutically effective amountxe2x80x9d will vary depending on the compound, the disease and its severity and the age, weight, etc., of the mammal to be treated.
The RARxcex3 agonist selectivity of a compound can be determined by routine ligand binding assays known to one of skill in the art such as described in C. Apfel et al. Proc. Nat. Sci. Acad. (USA), 89:7129-7133 (1992); M. Teng et al., J. Med. Chem., 40:2445-2451 (1997); and PCT Publication WO 96/30009.
The use of RAR agonists disclosed herein may be used for promoting the repair of damaged alveoli and septation of new alveoli, particularly for the treatment emphysema. Treatment with RAR agonists, particularly RARxcex3 selective agonists, is useful to promote repair of alveolar matrix and septation. As such, the methods disclosed herein are useful for treating diseases such as emphysema.
Typically, the dosage will range between about 0.01 and 1.0 mg/kg body weight per day, preferably from about 0.05 to about 0.5 mg/kg body weight per day.
In particular dosage of a RAR selective agonist required to treat lung emphysema will depend on the severity of the condition. This dosage may be delivered in a conventional pharmaceutical composition by a single administration, by multiple applications, or via controlled release, as needed to achieve the most effective results. Dosing will continue for as long as is medically indicated, which depending on the severity of the disease and may range from a few weeks to several months.
Typically, a pharmaceutically acceptable composition, such as a salt, of the RAR agonist of formula I in a pharmaceutically acceptable carrier or diluent is administered. In the context of the present invention, pharmaceutically acceptable salts include any chemically suitable salt known in the art of retinoid agonists as applicable for administration to human patients. Examples of conventional salts known in the art include the alkali metal salts such as sodium and potassium salts, the alkaline earth metal salts such as calcium and magnesium salts, and ammonium and alkyl ammonium salts.
Representative delivery regimens include oral, parenteral (including subcutaneous, intramuscular and intravenous), rectal, buccal (including sublingual), transdermal, pulmonary and intranasal. One method of pulmonary administration involves aerosolization of an aqueous solution of an RAR agonist. Aerosolized compositions may include the compound packaged in reverse micelles or liposomes. Typical pulmonary and respiratory delivery systems are described in U.S. Pat. Nos. 5,607,915, 5,238,683, 5,292,499, and 5,364,615.
The treatment methods of this invention also include systemic administration of RAR agonists in simultaneous or sequential combination with a further active ingredient.
RAR agonists will typically be administered as pharmaceutical compositions in admixture with a pharmaceutically acceptable, non toxic carrier. As mentioned above, such compositions may be prepared for parenteral (subcutaneous, intramuscular or intravenous) administration, particularly in the form of liquid solutions or suspensions; for oral or buccal administration, particularly in the form of tablets or capsules; for intranasal administration, particularly in the form of powders, nasal drops or aerosols; and for rectal or transdermal administration. Any conventional carrier material can be employed. The carrier material can be any organic or inorganic carrier material, such as water, gelatin, gum arabic, lactose, starch, magnesium stearate, talc, polyalkylene glycols, petroleum jelly and the like.
Liquid formulations for parenteral administration may contain as excipients sterile water or saline, alkylene glycols such as propylene glycol, polyalkylene glycols such as polyethylene glycol, oils of vegetable origin, hydrogenated naphthalenes and the like. They may employ slightly acidic buffers in pH ranges of about 4 to about 6. Suitable buffers include acetate, ascorbate and citrate at concentrations ranging from about 5 mM to about 50 mM. For oral administration, the formulation can be enhanced by the addition of bile salts or acylcarnitines.
Formulations for nasal administration may be solid and may contain excipients, for example, lactose or dextran, or may be aqueous or oily solutions for use in the form of nasal drops or metered spray. Particular nasal formulations include dry powders suitable for conventional dry powder inhalers (DPI""s), liquid solutions or suspensions suitable for nebulization and propellant formulations suitable for use in metered dose inhalers (MDI""s). For buccal administration typical excipients include sugars, calcium stearate, magnesium stearate, pregelatinated starch, and the like.
When formulated for nasal administration, the absorption across the nasal mucous membrane may be enhanced by surfactant acids, such as for example, glycocholic acid, cholic acid, taurocholic acid, ethocholic acid, deoxycholic acid, chenodeoxycholic acid, dehydrocholic acid, glycodeoxycholic acid, cyclodextrins and the like in an amount in the range between about 0.2 and 15 weight percent, preferably between about 0.5 and 4 weight percent, most preferably about 2 weight percent.
Solid forms for oral administration include tablets, hard and soft gelatin capsules. pills, sachets, powders, granules and the like. Each tablet, pill or sachet may contain from about 1 to about 50 mg, preferably from 5 to about 10 mg of RAR agonist of formula I. Preferred solid oral dosage forms include tablets, two-piece hard shell capsules and soft elastic gelatin (SEG) capsules. SEG capsules are of particular interest because they provide distinct advantages over the other two forms (see Seager, H., xe2x80x9cSoft gelatin capsules: a solution to many tableting problemsxe2x80x9d; Pharmaceutical Technology, 9, (1985)). Some of the advantages of using SEG capsules are: a) dose-content uniformity is optimized in SEG capsules because the drug is dissolved or dispersed in a liquid that can be dosed into the capsules accurately b) drugs formulated as SEG capsules show good bioavailability because the drug is dissolved, solubilized or dispersed in an aqueous-miscible or oily liquid and therefore when released in the body the solutions dissolve or are emulsified to produce drug dispersions of high surface area and c) degradation of drugs that are sensitive to oxidation during long-term storage is prevented due to the dry shell.
Delivery of the compounds of the present invention to the subject over prolonged periods of time, for example, for periods of one week to one year, may be accomplished by a single administration of a controlled release system containing sufficient active ingredient for the desired release period. Various controlled release systems, such as monolithic or reservoir type microcapsules, depot implants, osmotic pumps, vesicles, micelles, liposomes, transdermal patches, iontophoretic devices and alternative injectable dosage forms may be utilized for this purpose. Localization at the site to which delivery of the active ingredient is desired is an additional feature of some controlled release devices, which may prove beneficial in the treatment of certain disorders.
The following are representative pharmaceutical formulations for using RAR selective agonists as described herein for promoting elastin mediated matrix repair and alveolar septation.
The following preparations and examples are given to enable those skilled in the art to more clearly understand and to practice the present invention. They should not be considered as limiting the scope of the invention, but merely as being illustrative and representative thereof.
Tablet Formulation
The following ingredients are mixed intimately and pressed into single scored tablets.
Capsule Formulation
The following ingredients are mixed intimately and loaded into a hard-shell gelatin capsule.
Suspension Formulation
The following ingredients are mixed to form a suspension for oral administration.
Injectable Formulation
The following ingredients are mixed to form an injectable formulation.
Nasal Formulation
The following ingredients are mixed to form a suspension for nasal administration.
The compounds prepared in the following examples have been prepared as racemic mixtures. However, the racemic mixtures can be easily resolved into the respective enantiomers according to well established methods, e.g. at the stage of the 2,3,4,5-tetrahydrobenzo[b]oxepinyl-methanol or 2,3,4,5-tetrahydrobenzo[b]thiepinyl-methanol, respectively. Such methods include separation by HPLC on a chiral column, e.g. a chiral NUCLEOSIL column; or separation by derivatization with a chiral acid, e.g. Mosher""s acid, separation of the corresponding diastereomers by conventional techniques followed by reductive or hydrolytic cleavage of the ester.